<!DOCTYPE html>
<meta charset="utf-8">
<style>

.links line {
  stroke: #999;
  stroke-opacity: 0.6;
}

.nodes circle {
  stroke: #fff;
  stroke-width: 1.5px;
}

</style>
<svg width="600" height="600"></svg>
<script src="./d3.min.js"></script>
<script>

var svg     = d3.select("svg"),
    width   = +svg.attr("width"),
    height  = +svg.attr("height");

var color   = d3.scaleOrdinal(d3.schemeCategory10);

var simulation = d3.forceSimulation()
    .force("link", d3.forceLink().id(function(d) { return d.id; }))
    .force("charge", d3.forceManyBody())
    .force("center", d3.forceCenter(width / 2, height / 2));
    // .force('chargeDistance', function(d) { return 19999});

d3.json("graph.json", function(error, graph) {
  if (error) throw error;

  var link = svg.append("g")
      .attr("class", "links")
      .selectAll("line")
      .data(graph.links)
      .enter().append("line")
        .attr("stroke-width", function(d) { return 1 });

  var node = svg.append("g")
      .attr("class", "nodes")
      .selectAll("circle")
      .data(graph.nodes)
      .enter().append("circle")
        .attr("r", 10)
        .attr("fill", function(d) { return color(d.group); })
        .call(d3.drag()
            .on("start", dragstarted)
            .on("drag", dragged)
            .on("end", dragended));
  
  //Add the SVG Text Element to the svgContainer
  var text = svg.append("g")
                .attr("class", "text")
                .selectAll("text")
                .data(graph.nodes)
                .enter()
                .append("text")
                 .text( function (d) { return d.name; })
                 .attr("font-size", "15px")
                 .attr("fill", "black");            
  
  node.append("title")
      .text(function(d) { return d.name; });

  simulation
      .nodes(graph.nodes)
      .on("tick", ticked);


  simulation.force("link")
      .links(graph.links).distance(function(d) {return 100});


  function ticked() {
    link
        .attr("x1", function(d) { return d.source.x; })
        .attr("y1", function(d) { return d.source.y; })
        .attr("x2", function(d) { return d.target.x; })
        .attr("y2", function(d) { return d.target.y; });
    
    text
        .attr("dx", function(d) { return d.x-20; })
        .attr("dy", function(d) { return d.y; });

    node
        .attr("cx", function(d) { return d.x; })
        .attr("cy", function(d) { return d.y; });
  }
});

function dragstarted(d) {
  if (!d3.event.active) simulation.alphaTarget(0.3).restart();
  d.fx = d.x;
  d.fy = d.y;
}

function dragged(d) {
  d.fx = d3.event.x;
  d.fy = d3.event.y;
}

function dragended(d) {
  if (!d3.event.active) simulation.alphaTarget(0);
  d.fx = null;
  d.fy = null;
}

</script>